That cost usually is shorter plays. The problem is, those shorter plays sometimes bust out for huge plays if the tackling is poor.
Lately, the tackling has been poor.
First-round rookie Fletcher Cox, who will start at tackle alongside Cullen Jenkins, might be the second coming of Jerome Brown. But Cox has not seen a full-speed, bowed-up, for-the-cash NFL double team, which Jerome Brown ate for lunch. Certainly, Cox has not seen a grown-man double-team on four straight plays.
He might absorb it. He might beat it.
He might disappear.
Undrafted last season out of Division II Southern Arkansas, a fine rodeo school, Thornton hasn't even seen a full-speed Division I double team. He might absorb it. Or beat it. Or disappear.
Dixon often absorbed it. But he seldom beat it.
He occasionally disappeared.
Dixon was not a dynamic player, not even at Miami. He was just steady, and big. That mule doesn't make it in the wide-9 scheme.
As a Mulerider, Thornton spent most of his games in the other teams' backfield. That's a good thing on any level.
Nevertheless, once again, the Eagles opted for the sports car over the dump truck.
Perhaps they cannot remember how Frank Gore and Marshawn Lynch destroyed their playoff hopes. Gore came alive for the 49ers after Dixon left that game. Lynch was the Seahawks' only hope.
True, Dixon was around for the ferocious, early ground-game beatings handed to the Eagles by the Falcons and Giants, but the scheme was altered just a bit by Game 4.
In the absence of veteran Mike Patterson, lost perhaps for the season as he recovers from brain surgery, Dixon at least would have been a known entity.
In the Andy Reid era, the Eagles have placed as little value on stopping the run as they have placed on covering the slot receiver.
They cut valuable nickel corner Joselio Hanson after camp last season . . . then hurriedly re-signed him when no others became available.
The plan: Move speed demon Dominique Rodgers-Cromartie to the slot.
The plan stunk. DRC never got the hang of it. The Eagles were their best when Hanson played in place of DRC, who sat for 3 weeks with an ankle injury, then the final 2 weeks, when Hanson got injured Asante Samuel's spot.
Last week, they cut Hanson again.
This time, he went home, to California, where he signed with Oakland.
The weight of covering hot-read slot receivers falls to Brandon Boykin, a fourth-round pick out of Georgia.
There, like virtually anyone drafted by an NFL team, Boykin did not play the nickel. Playing nickel is like pitching the eighth inning; you get all the pressure of closing but none of the money or recognition. And you never get that job until someone else fails.
Or gets cut.
Keeping Boykin was an easy decision. He is a valuable special-teams player; Hanson was not. Boykin is agile and compact, like Hanson; the pair share nearly identical dimensions, but Boykin is, perhaps, a few pounds heavier, with room to grow.
Boykin also is about $450,000 cheaper.
The other considerations at defensive back: corner Brandon Hughes, who proved himself a fine special-teams player; corner Curtis Marsh, a little-used third-round pick last year, but a third-round pick nonetheless; safety Jaiquawn Jarrett, a second-rounder in the same situation; and safety Colt Anderson, while returning from injury, was the best special-teamer in 2011.
Somebody had to go.
Logic dictated it be Hanson.
Understand: Neither of these moves is likely to keep the Eagles from the Super Bowl. Any team that is a fourth tackle or third cornerback away from being the best in the league is not close to being the best in the league.
But, depending on how their replacements play, either could cost the Birds a win. Maybe two.
That is the price of saving money.
The price of developing youth.
It is a price the Eagles paid last season, when they opted to misuse three star-caliber corners instead of simply sitting one of them in deference to Hanson.
It is a price they paid when the Niners and Seahawks upset them by pounding the ball down their gullet.
A loss here or there could mean no playoffs, if that is the minimal goal.
No playoffs in 2012 means no more Reid, and, with him, his three top assistants and his line coaches.
No more Michael Vick.
It means essentially, blowing up the organization.
Suddenly, there's a lot more pressure on Cox and Thornton and young Boykin.
Contact Marcus Hayes at email@example.com. For recent columns, go to www.philly.com/MarcusHayes.